A heat sink is a common component for thermal management. Heat sinks are used in a variety of applications and industries and are usually made of aluminium, copper or ceramic.
Heat sinks are lightweight, easy to customize and can be produced in a range of profiles to offer the most effective cooling for the device. The basic design comprises of a flat base plate with a series of fins protruding from it to increase the overall surface area of the component. Heat sinks usually have straight fins, cross-cut fins, pin fins or flared pins.
How does a heat sink work?
Heat sinks dissipate heat from the source using the basic principles of conduction and convection. They have a large surface area where the heat is initially spread over before being transferred away from the heat source by the fins and the working fluid. The working fluid is usually air but may also be a non-conductive liquid. This process relies on the temperature gradient of the heat sink and the ambient temperature surrounding it.
Heat sinks can be defined as passive, active or hybrid with each set up offering its own advantages and considerations.
Passive heat sinks use natural convection, which means the density of the working fluid is enough to dissipate heat away from the heat sink without the need for additional components or systems to achieve cooling.
Active heat sinks use forced air to increase fluid flow across the heat sink, this is usually achieved by using a fan but can also be from movement of the component itself. Both approaches increase heat dissipation by allowing more unheated air to flow over the heat sink, increasing the total thermal gradient across the system.
Hybrid heat sinks combine elements from both passive and active heat sinks and utilise control systems to cool components. When the device reaches a set temperature the active cooling mechanism kicks in to return the device to its preferred temperature range, once cooling has been achieved the device reverts back to passive thermal management through the heat sink.
There are a number of methods used to fix the heat sink in place, these include thermal tapes such as the TG-T1000T which provides exceptional bonding properties and eliminates the need for mechanical fasteners whilst also offering flexibility for repositioning or reuse.
Push pins with compression springs are usually used on larger heat sinks with higher preloads. The push pins have a flexible barb that pushes through a hole in the PCB and is then held in place by the springs.
Screws are usually used for very large heat sinks and usually comprise of a threaded standoffs with springs, this approach for fastening is the most costly.
In order to optimise the efficiency and performance of the heat sink and the device thermal interface materials such as putties, greases or pads can be used to provide a heat path between the device and the heat sink where microscopic air gaps and uneven surface texture impedes good thermal transfer.
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